Danish research has linked perceived age within twins to life expectancy (Photograph: SPL)

The study, published in the Christmas issue of the BMJ, examined whether perceived age is linked with survival and important age-related traits, such as physical and cognitive functioning and leukocyte telomere length, a marker of ageing.

In spring 2001, 1,826 Danish twins aged 70 years and over underwent physical and cognitive tests and had their faces photographed.

Death records were then used to track the survival of the twins over a seven-year period.

Overall, perceived age was significantly associated with survival, even after adjusting for chronological age, sex, and the environment in which each pair of twins grew up.

The bigger the difference in perceived age within a twin pair, the more likely it was that the older looking twin died first.

The researchers from the University of southern Denmark believe that common genetic factors influencing both survival and perceived age may help to explain these results.